1. Field of the Invention
The present invention relates to a medical image display apparatus, method and program for displaying three-dimensional volume data and a functional image of a subject.
2. Description of the Related Art
Conventionally, a medical image display apparatus having a mode for observing the inner wall of a lumen of a subject as if seeing it from the inside of the lumen has been known. In this mode, an image of a three-dimensional structure is obtained by volume rendering based on three-dimensional digital data of an object obtained by CT or the like, and an image resembling an endoscopic image is generated based on the three-dimensional volume data to observe a lesion in a tubular organ, such as a blood vessel, intestines, bronchi and an artery, of the subject. Further, as three-dimensional image processing, MIP (Maximum Intensity Projection) processing, MinIP (Minimum Intensity Projection) processing, MPR (Multi Planar Reconstruction) processing, CPR (Curved Planaer Reconstruction) processing, and the like are known. Especially, the CPR processing selects an arbitrary surface in three-dimensional volume data, and reconstructs a two-dimensional image from a three-dimensional image along the selected surface. Accordingly, with respect to the morphology of the inner wall of a tubular structure, such as a large intestine and a blood vessel for example, it is possible to display a cross section of the tubular structure in a longitudinal direction thereof on a display screen (for example, please refer to Japanese Unexamined Patent Publication No. 2007-135843 (Patent Document 1) and Japanese Unexamined Patent publication No. 2004-283373 (Patent Document 2)).
Besides a morphological image obtained from the CT apparatus or the like, and which represents the morphology of the subject, a functional image representing the function of the subject is provided for a user. As the functional image, for example, a SPECT image obtained by Single Photon Emission Tomography, a PET image obtained by Positron Emission Tomography, an analysis result, such as a bull's eye image, obtained by analyzing a morphological image and a functional image, and the like are known.
As a method for displaying the aforementioned morphological image and functional image, a method for displaying the morphological image and the functional image one on the other is known (for example, please refer to Japanese Unexamined Patent Publication No. 2006-198060 (Patent Document 3)). Patent Document 1 discloses displaying a functional image and a morphological image one on the other after a relative positional relationship between the functional image and the morphological image is obtained, and coordinate transformation is performed to match the size of the functional image and that of the morphological image based on the relative positional relationship.
However, when the functional image and the morphological image are simply placed one on the other as disclosed in Patent Document 1, the function of each region of a subject may be recognized, but there is a problem that the efficacy of diagnosis becomes lower because the morphology of the subject is hard to recognize. For example, when a SPECT image or the like is displayed on a CPR image of a blood vessel or the like obtained from a morphological image, such as a CT image, if the SPECT image or the like is simply displayed in such a manner to be placed directly on the CPR image, observation of morphology information, such as a stenosis condition and a plaque site of a blood vessel, becomes difficult because the images are placed one on the other. Meanwhile, even if the functional image and the morphological image are separately displayed, there is a problem that the function of each region is not recognizable at a glance.